/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.BoundType.CLOSED;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.Serializable;
import java.util.Collection;
import javax.annotation.Nullable;

/**
 * An implementation of {@link ContiguousSet} that contains one or more elements.
 *
 * @author Gregory Kick
 */
@GwtCompatible(emulated = true)
@SuppressWarnings("unchecked") // allow ungenerified Comparable types
final class RegularContiguousSet<C extends Comparable> extends ContiguousSet<C> {
    private final Range<C> range;

    RegularContiguousSet(Range<C> range, DiscreteDomain<C> domain) {
        super(domain);
        this.range = range;
    }

    private ContiguousSet<C> intersectionInCurrentDomain(Range<C> other) {
        return (range.isConnected(other)) ? ContiguousSet.create(range.intersection(other), domain)
                : new EmptyContiguousSet<C>(domain);
    }

    @Override
    ContiguousSet<C> headSetImpl(C toElement, boolean inclusive) {
        return intersectionInCurrentDomain(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
    }

    @Override
    ContiguousSet<C> subSetImpl(C fromElement, boolean fromInclusive, C toElement, boolean toInclusive) {
        if (fromElement.compareTo(toElement) == 0 && !fromInclusive && !toInclusive) {
            // Range would reject our attempt to create (x, x).
            return new EmptyContiguousSet<C>(domain);
        }
        return intersectionInCurrentDomain(Range.range(fromElement, BoundType.forBoolean(fromInclusive), toElement,
                BoundType.forBoolean(toInclusive)));
    }

    @Override
    ContiguousSet<C> tailSetImpl(C fromElement, boolean inclusive) {
        return intersectionInCurrentDomain(Range.downTo(fromElement, BoundType.forBoolean(inclusive)));
    }

    @GwtIncompatible // not used by GWT emulation
    @Override
    int indexOf(Object target) {
        return contains(target) ? (int) domain.distance(first(), (C) target) : -1;
    }

    @Override
    public UnmodifiableIterator<C> iterator() {
        return new AbstractSequentialIterator<C>(first()) {
            final C last = last();

            @Override
            protected C computeNext(C previous) {
                return equalsOrThrow(previous, last) ? null : domain.next(previous);
            }
        };
    }

    @GwtIncompatible // NavigableSet
    @Override
    public UnmodifiableIterator<C> descendingIterator() {
        return new AbstractSequentialIterator<C>(last()) {
            final C first = first();

            @Override
            protected C computeNext(C previous) {
                return equalsOrThrow(previous, first) ? null : domain.previous(previous);
            }
        };
    }

    private static boolean equalsOrThrow(Comparable<?> left, @Nullable Comparable<?> right) {
        return right != null && Range.compareOrThrow(left, right) == 0;
    }

    @Override
    boolean isPartialView() {
        return false;
    }

    @Override
    public C first() {
        return range.lowerBound.leastValueAbove(domain);
    }

    @Override
    public C last() {
        return range.upperBound.greatestValueBelow(domain);
    }

    @Override
    ImmutableList<C> createAsList() {
        if (domain.supportsFastOffset) {
            return new ImmutableAsList<C>() {
                @Override
                ImmutableSortedSet<C> delegateCollection() {
                    return RegularContiguousSet.this;
                }

                @Override
                public C get(int i) {
                    checkElementIndex(i, size());
                    return domain.offset(first(), i);
                }
            };
        } else {
            return super.createAsList();
        }
    }

    @Override
    public int size() {
        long distance = domain.distance(first(), last());
        return (distance >= Integer.MAX_VALUE) ? Integer.MAX_VALUE : (int) distance + 1;
    }

    @Override
    public boolean contains(@Nullable Object object) {
        if (object == null) {
            return false;
        }
        try {
            return range.contains((C) object);
        } catch (ClassCastException e) {
            return false;
        }
    }

    @Override
    public boolean containsAll(Collection<?> targets) {
        return Collections2.containsAllImpl(this, targets);
    }

    @Override
    public boolean isEmpty() {
        return false;
    }

    @Override
    public ContiguousSet<C> intersection(ContiguousSet<C> other) {
        checkNotNull(other);
        checkArgument(this.domain.equals(other.domain));
        if (other.isEmpty()) {
            return other;
        } else {
            C lowerEndpoint = Ordering.natural().max(this.first(), other.first());
            C upperEndpoint = Ordering.natural().min(this.last(), other.last());
            return (lowerEndpoint.compareTo(upperEndpoint) <= 0)
                    ? ContiguousSet.create(Range.closed(lowerEndpoint, upperEndpoint), domain)
                    : new EmptyContiguousSet<C>(domain);
        }
    }

    @Override
    public Range<C> range() {
        return range(CLOSED, CLOSED);
    }

    @Override
    public Range<C> range(BoundType lowerBoundType, BoundType upperBoundType) {
        return Range.create(range.lowerBound.withLowerBoundType(lowerBoundType, domain),
                range.upperBound.withUpperBoundType(upperBoundType, domain));
    }

    @Override
    public boolean equals(@Nullable Object object) {
        if (object == this) {
            return true;
        } else if (object instanceof RegularContiguousSet) {
            RegularContiguousSet<?> that = (RegularContiguousSet<?>) object;
            if (this.domain.equals(that.domain)) {
                return this.first().equals(that.first()) && this.last().equals(that.last());
            }
        }
        return super.equals(object);
    }

    // copied to make sure not to use the GWT-emulated version
    @Override
    public int hashCode() {
        return Sets.hashCodeImpl(this);
    }

    @GwtIncompatible // serialization
    private static final class SerializedForm<C extends Comparable> implements Serializable {
        final Range<C> range;
        final DiscreteDomain<C> domain;

        private SerializedForm(Range<C> range, DiscreteDomain<C> domain) {
            this.range = range;
            this.domain = domain;
        }

        private Object readResolve() {
            return new RegularContiguousSet<C>(range, domain);
        }
    }

    @GwtIncompatible // serialization
    @Override
    Object writeReplace() {
        return new SerializedForm<C>(range, domain);
    }

    private static final long serialVersionUID = 0;
}
